Pneumonia remains the most common reason for death or poor performance in growing calves, and whilst we do see a spike in the number of cases through the winter months, it is important to remember that it can occur at anytime of year and the long-term impacts can be significant. On average a case of pneumonia will reduce a heifers weight at 14 months by 29kg, will increase her age at first calving by 30 days and result in a reduction in her first lactation production of around 150kg.
So how can we minimise the risk of this disease? At the risk of sounding like a broken record it all starts with colostrum. Many of the disease outbreaks I get asked to get involved with are often traced back, at least in part, to issues with colostrum feeding. Colostrum provides immunoglobulins that provide the immunity the calf requires to fight disease in the first couple of months of life. A calf’s ability to absorb immunoglobulins is greatest immediately after birth. Changes in the cells within the calf’s intestine mean that by 24hrs of age the animal is no longer able to absorb the immunoglobulins from the colostrum, miss this opportunity and you will be fighting an uphill battle with the health of this heifer. As a rough rule aim to ensure every calf receives 3 litres of good quality colostrum within the first 2 hours of life followed by another similar size feed within 12 hours. Ensure all members of the team know exactly what your colostrum protocol is and make sure it is regularly reviewed. A simple blood test in the first week of life will be able to tell you whether your calves are receiving sufficient colostrum and can be carried out at regular point to monitor your colostrum feeding practices.
Pneumonia is a multifactorial problem and so addressing one area in isolation is unlikely to be the answer. We are lucky to have several very effective pneumonia vaccines at our disposal but even they will struggle to be effective if the environment is not right. Ventilation is essential to reduce the transmission of airborne pathogens from calf to calf and prevent damage to the respiratory system by dust or noxious gases. Most calf sheds in the UK rely on natural ventilation as their source of fresh air with air movement being driven by pressure differences created by wind movement around the shed. Depending on the shed location and the prevailing winds this will lead to a huge amount of variability on how a shed ventilates, often with significant periods of time when the supply of fresh air is compromised. The stack effect is often discussed as another potential driver of air movement within calf sheds, however the stack effect is reliant on the heating effect of stock, and young calves will not produce sufficient heat to drive the air movement up and out of the shed.
However a shed is ventilated, the aim should be to achieve at least 4 air changes per hour. Smoke bombs (available from your local plumbers’ merchant) are a quick and easy way of visualising air movements within sheds and can be used to identify problem areas. Over the last few years there has been a resurgence in the use of Positive Pressure Air Tube Systems (PPAT) which provide a cost-effective way of delivering fresh air into calf sheds. The PPAT system consists of a wall-mounted fan blowing fresh outside air into the shed. Attached to the fan is a distribution tube with equally spaced holes in it that runs the length of the shed. The fan draws fresh air in from the outside, pressurizing the tube and blowing the air out of each of the holes to distribute it evenly throughout the shed. The PPAT requires careful set up and design to ensure that the air is evenly distributed throughout the shed and to avoid creating any artificial draughts by introducing the air too quickly.
Stress is another major risk factor for disease as it results in a suppression of the calf’s immune system. We frequently see pneumonia outbreaks immediately after a stressful event such as transport, weaning or other handling so systems should be designed to minimise stress and always ensure you have good handling facilities.
Even in the best systems the risk of disease can never be 100% eliminated so it is important to remain ever vigilant and ensure that cases are rapidly identified and treated appropriately. The common signs of pneumonia are well known (coughing, weeping eyes, breathing difficulties) but these are often not the first signs. Look out for reduction in feed intake, separation from the other calves and increased lying times. Rectal temperature can be used to check animals that you are concerned about; a temperature of 39.5oC or above is a good indicator of infection and treatment should be administered in line with the protocols agreed with your vet.
Written by Tim Potter BVetMed PhD MRCVS. First published in South East Farmer.